Tali was born aboard the starship Rayya in 2161. Upon reaching maturity, Tali left the Migrant Fleet to initiate her Pilgrimage. While traveling through the galaxy, Tali began to hear rumors of Geth venturing outside of the Perseus Veil. The Quarian people have held a grudge against the Geth ever since they were driven from their homeworld by the machines. Tali began to investigate these rumors, which led her to an uncharted planet where she tracked a patrol of Geth. She was able to disable an isolated Geth and remove its memory core. The memory core contained an audio file that revealed that Saren Arterius was responsible for the attack on the Human colony of Eden Prime. In an attempt to cover his tracks, Saren ordered his forces to hunt down Tali and recover the data. Tali fled to the Citadel in the hope of finding a safe haven.

During her escape to the Citadel, Tali received a gunshot wound. She made her way to Dr. Chloe Michel's Med Clinic to get treatment. She told Dr. Michel that she wanted to meet with the Shadow Broker in order to exchange the information for a safe hiding place. However, the Shadow Broker's agent, Fist double-crossed Tali who revealed himself to be working for Saren. Instead of meeting with the Shadow Broker's agents, Tali came into contact with a group of assassin's. Tali threw a tech proximity mine in an attempt to defend herself. She was then rescued by Shepard who killed the assassin's.

Upon joining Shepard's team, Tali moves into the Normandy's engine room. She spends a lot of time with Engineer Adams, who is impressed with her vast knowledge of engines and starships. He wishes that his team were even half as smart as her. Tali and Adams usually work together to dismantle any technology or resources that the Normandy acquires through survey missions. Shepard can talk with Tali Tali, who reveals that she is fascinated by the Normandy, especially its stealth systems and drive core.

Tali reveals more about Quarian life. She tells Shepard about her Pilgrimage and the three century old ships that make up a majority of the Migrant Fleet. She reveals that her mother died only five years prior to meeting Shepard and that she misses her. Her mother died due to the effects of an airborne virus that struck the Flotilla. Tali also reveals that her father is the head of the Admiralty Board, which is the highest level of Quarian authority. As such, people are expecting Tali to accomplish great things while on her Pilgrimage.

Shepard can also converse with Tali about the Geth and their origins. She tells him that they were originally created to serve as workers for the Quarian race. She also tells that the Geth eventually developed to a level the Quarians did not expect. They began to question their existence. The Quarians struck first to prevent an eventual Geth attack. They believed that as the Geth were beginning to show signs of sentience, that would label them as slaves. However, the Geth rebelled against their masters, leading to a war which took the lives of millions of Quarians. Shepard can debate this subject with her, pointing out the fact that the Quarians had attempted genocide against another sentient race.

Initially Tali is excited to be aboard one of the most advanced ships in the galaxy, but soon begins to encounter problems. She tells Shepard that she finds it difficult to sleep due to how quiet the Normandy is. Quarian ships are usually very loud, with silence meaning that an engine has died. She is becomes homesick, missing the crowded lifestyle she had on the Flotilla. She believes that the Normandy is uneasily empty. Over time she becomes accustomed to life aboard the Normandy and starts to feel more relaxed. When traveling through the Citadel, Tali reveals that she loves the crowds, which reminds her of home. She also expresses delight when hearing the music at Flux, hoping to take a copy back with her.

If Shepard is respectful of Tali, she thanks him, claiming that most people treat Quarains as second-class citizens. Tali finds it exhilarating traveling to Ilos after stealing the Normandy. However, she is worried about the consequences they will face if caught by the Citadel Fleet. Shepard tells her that her father could get her relieved of all charges. However, Tali claims that stealing a ship is one of the greatest offenses a Quarian can commit, a crime punishable by death. She believes that her father would "probably want to execute us himself".

If Tali accompanies Shepard to Ilos, she claims that the planet is disturbing. She also reveals that the Quarians had attempted to find Ilos at one stage, believing it to be a potential homeworld. When the squad confronts Vigil, Tali is saddened by the revelation of the Protheans extinction. Like the Quarians, they tried to fight the machines, only to lose everything.

After a mission in the Armstrong Nebula, Shepard finds a terminal which details the earliest days of the Geth.

When Shepard returns to the Normandy, Tali asks if she can have a copy. She believes that it will take years to fully decode the data, but it would be an excellent gift for her Pilgrimage. Shepard can reuse to give her a copy of the data, claiming that it is classified Alliance information. She claims that she will stay to help fight Saren, but afterwards she must leave to find something of value to complete her Pilgrimage.

Alternatively, Shepard can give Tali a copy of the data, which makes her happy. The data will allow her to return to her people and complete her Pilgrimage. However, she promises Shepard that she will stay with him until they defeat Saren.

Following the completion of her Pilgrimage and the Collector attack on the Normandy, Tali became a crew member of the starship Neema. This effectively changed her name to Tali'Zorah vas Neema. She was given a new body suit as a symbol of her maturity. Tali quickly began to become a well known and respected member of the Migrant Fleet. In 2185, Tali led team to the Human colony of Freedom's Progress. Her mission was to locate another Quarian, Veetor'Nara, who had been helping the colonists as part of his Pilgrimage. After the colony went silent, he was listed as missing. Tali landed on the planet, only to find the colony was empty, save for a few hostile Mechs. Tali deemed that the Mechs were being controlled by Veetor. While searching through the colony, Tali and her team ran into Shepard. Shepard was being accompanied by Jacob Taylor and Miranda Lawson in an investigation into the colony. Tali believed Shepard had died two years ago at the Normandy's destruction.

Initially, Tali was happy and excited to see Shepard, but this quickly changed. Tensions were soon raised when it was revealed that Shepard was working with Cerberus. Tali opposed Cerberus due to their anti-alien beliefs and their recent attack on the Flotilla. Tali forced herself to believe that Shepard was only working undercover, and planned to bring Cerberus down after the investigation. It was decided that the two teams would split, being able to search the colony faster. Tali's team became anxious, not wanting Veetor to be taken by Cerberus. They rushed ahead and were attacked by a YMIR Mech, which killed most of the team. Shepard destroyed the Mech, while Tali tended to the wounded. Shepard found a distressed Veetor. He was able to provide Shepard with evidence that proved the Collector's were responsible for the attack. Shepard then had to choose between handing Veetor over to Cerberus for investigation, or allow him to return to the Flotilla after taking data from his omni-tool. Tali disapproves if Shepard takes Veetor into Cerberus custody. Alternatively, she thanks Shepard for helping her find Veetor. Regardless of Shepard's decision, Tali returns to the Flotilla. Tali tells Shepard that she has an important mission that she must attend to, which involves entering Geth-controlled space.

Tali's involved infiltrating the planet Haestrom to investigate the planets dying star. The star, Dholen, is maturing into a red giant, despite being normal 100 years previous. Tali was accompanied by a group of elite Quarian marines, led by Kal'Reegar, whom were to combat any Geth resistance.The mission took a turn for the worst when a Geth patrol ship spotted the team and began dropping of Geth units. The majority of the marines were killed and Tali was locked inside the building containing the information she had gathered. However, Shepard traveled to Haestrom in hopes of recruiting Tali. He began fighting the Geth, eventually coming into contact with Kal'Reegar.

As Shepard came closer to finding Tali, the rest of the marine were killed fending of the Geth from taking their position. Shepard Was able to fight through the Geth, meeting up with Kal'Reegar. He informed Shepard that Tali's position was being guarded by a Geth Colossus. Reegar had gained its attention by firing missiles at it, slowing down the Geth. Shepard can allow Reegar to continue to attack the Geth Colossus, in which case he dies during the attack. Shepard can also convince him to stay back and cover their rear-guard. Shepard is able to destroy the Colossus and free Tali.

Tali explained that the data she was able to gather proved that the sun was dying too quickly, due to the involvement of dark energy which is affecting the mass of the star. Tali is saddened by the deaths of the marines, claiming that many of them were her friends. She angrily hoped that the Admiralty Board would use the data effectively. If Kal'Reegar survived the attack, she thanks Shepard for helping him and informs Reegar that she is leaving with Shepard.

When brought back aboard the Normandy, Tali is welcomed by Jacob. However, Tali brushes off the warm welcome, showing her distrust for Cerberus. Tali claims that she is joining the mission to aid Shepard, not Cerberus, reminding Shepard of Cerberus' previous actions. She shows disgust at their experiments of Thorian Creepers and Rachni. As she leaves, Jacob tells her to introduce herself to EDI, the Normandy's AI. This leaves her even more perplexed.

After the Normandy enters the Omega 4 Relay, the ship is attacked by Collector Oculus sentries. If Shepard didn't research the shields that Tali can upgrade the Normandy with, she can be killed in an explosion in the engineering deck after Joker is forced to plough the Normandy through a debris field. If she survives the Oculus attack, Tali takes part in the attack on the Collector base.

If Shepard has gained Tali's Loyalty, she can be chosen to proceed through the ventilation system and open the various doors of the base, allowing Shepard to continue. If Tali i brought to the fight against the Human-Reaper Larva, she claims that Shepard should destroy the base, showing disgust at the Collectors actions.

Tali is a potential romance option for Shepard. After joining the Normandy's crew, Kelly informs Shepard of Tali's body language when around him, suggesting that she is attracted to him. After the completion of Tali's Loyalty mission, Shepard can begin romancing her. Tali reveals that she has been harboring feelings for Shepard since their mission to stop Saren. She believes that he would never understand her and so never moved upon her feelings. However, she is excited when Shepard claims to also have feelings for her. Tali later claims that she shouldn't have confessed her feelings and that Shepard should be free to choose whomever he likes. However, Shepard claims that he only wants her, and will do anything for her.

Tali wishes to have a more intimate relationship with Shepard, saying that she wants to "feel his skin against hers." This is problematic, however, as Quarians have a weak immune system and their dextro-DNA can prove any physically intimate contact fatal. Tali asks Shepard to allow her time to prepare.

Before entering the Omega 4 Relay, Tali enterms Shepard's quarters, claiming that she has taken anti-biotics and herbal supplements to help her immune system when her suit is removed. She begins to grow nervous and begins speaking continuously, claiming it is a "defense mechanism." She is afraid to remove her bio-suit and reveal her face to Shepard, who then removes her helmet, and sees her face for the first time. Tali then jumps on top of Shepard and the scene fades to black.

If both Shepard and Tali survive the suicide mission, she informs Shepard that she is "running a fever," has a "nasty cough," and her sinuses "are filled with something she can't even describe." However she claims that it was "totally worth it."